Positive-type electron multiplier channels connected in series



April 4, 1970 D. H. :-EcKowsK| ETAL 3,506,868

POSITIVE-TYPE ELECTRON MULTIPLE CHANNEL CONNECTED IN SERIES I OriginalFiled Sept. 30, 1963 NPUT 'IIIIIIIIIIIIIIIIIIIIIIIA l8 zooov l4 -||sov-3oov l T DIRECT VOLTAGE SOURCE INVENTOR DONALD H. CECKOWSKI GEORGE wsooomcu BY ANDREW J. MEYER United States Patent 3,506,868 POSITIVE-TYPEELECTRON MULTIPLIER CHANNELS CONNECTED IN SERIES Donald H. Ceckowski,Ferndale, George W. Goodrich,

Oak Park, and Andrew J. Meyer, Birmingham, Mich.,

assignors to The Bendix Corporation, a corporation of DelawareContinuation of application Ser. No. 312,414, Sept. 30,

1963. This application May 22, 1967, Ser. No. 640,428 Int. Cl. H01j39/16, 43/18 US. Cl. 313103 11 Claims ABSTRACT OF THE DISCLOSURE Aplural section electron multiplier device having separate-strip portionsfor providing improved gain and resolution. The purpose of the foregoingabstract is to enable the Patent Office and the public generally andespecially the scientist, engineer, or practitioner in the art who isnot familiar with patent or legal terms or phraseology to determinequickly from a cursory inspection the nature and essence of thetechnical disclosure of the application. The abstract is neitherintended to define the invention of the application, which of course ismeasured by the claims nor is it intended to be limiting as to the scopeof the in vention in any Way.

This application is a continuation of application, Ser. No. 312,414,filed Sept. 30, 1963.

This invention relates to channel electron multipliers and moreparticularly to channel electron multipliers disposed in seriesrelationship for amplifying a radiation image.

In copending patent application U.S. Ser. No. 23,574, filed Apr. 20,1960, by George W. Goodrich and W. C. Wiley, there is fully disclosed atube type channel electron multiplier. In this type multiplier, theinside surface of the tube is resistive and has secondary emissiveproperties. Upon the application of a voltage difference between theends of the tube, current flows through the inner resistive surfaceproducing an electric field in an axial direction through the regiondefined by the tube. Electrons or particles of suitable energy enteringthe input end of the tube are multiplied through secondary emissionbefore they emerge from the output end of the tube.

In multipliers of this type, the output current is limited by themagnitude of current through the resistive inner surface referred to asstrip current, since it is this current which supplies the electrons inthe secondary emis sion process. However, the strip current cannot beincreased without limit to obtain greater output currents because atsome point the amount of heat generated in the strip will exceed theequilibrium heat dissipation characteristics of the multiplier andthermal runaway will occur, eventually destroying the multiplier. Thus,the output current of a channel electron multiplier is governed by themagnitude of available strip current, subject to a limitation imposed byits thermal dissipation characteristics.

One method of surmounting the relatively low output current capabilitiesof a single channel multiplier is simply to increase the surface area ofthe tube with a corresponding decrease of inner surface resistance. Inthis way, a larger strip current can be carried; a greater amount ofheat can be dissipated through the increased channel surface area, and ahigher output current will be achieved. However, in certainapplications, for example star tracking devices, where a single channelhaving an input diameter of 0.020 inch or smaller is dictated by opticalresolution requirements, the relatively low output current of thechannel limits the efiectiveness of the tracking device.

That is, a single channel having a length to diameter ratio of 60:1 andan input diameter of 0.020 inch typically produces a stable maximumoutput current of only 0.2 microampere.

In accordance with this invention, higher output currents are obtainedby disposing continuous channel electron multipliers in seriesrelationship to overcome the disadvantageous low output currentlimitation of a single channel of required resolution capability. Afirst channel having required resolution capability has disposed at itsoutput a second channel having a larger diameter and greater stripcurrent carrying capacity than the first. In this way, an advantage isachieved whereby the output current of the two channels is substantiallyhigher than the output current of a single channel multiplier of thesame resolution capability as the first channel.

For example, a 0.020 inch first channel of 30:1 length to diameterratio, and a 0.30 inch second channel of 30:1 length to diameter ratioare capable of producing an output current of 2.0 microamperes, animprovement of a decade over a single 0.020 inch channel multiplier of60:1 length to diameter ratio. Of course, in the example given, thetotal length of the two channels is 1.500 inches whereas the totallength of the single channel is only 1.200 inches. This disadvantage,however, is easily surmounted by the substantially greater outputcurrent obtained from the first and second channels.

An object of this invention is to provide channel electron multipliersarranged in series for the amplification of radiation images.

Another object of this invention is to provide a first channelresolution element position to direct its output current into a secondchannel of larger diameter.

Other objects and advantages will become apparent from the followingdetailed description and from the appended drawings and claims.

In the drawings:

FIGURE 1 is a perspective view, partly broken away illustrating anembodiment of this invention.

FIGURE 2 is a schematic diagram illustrating the embodiment in FIGURE 1and showing the associated electrical circuitry and resultant electronpaths.

In FIGURE 1, a channel electron multiplier 2 is positioned to receiveparticles, such as ions or electrons, from a source (not shown). Forexample, the channel 2 may receive electrons from a photocathode.Positioned at the output of the channel 2 is another channel electronmultiplier 4 of larger diameter. Thus, the output current of channel 2provides the input current for channel 4. This input current issubsequently multiplied and collected by the anode 6 which is disposedrelative to the output end of channel 4 to collect electrons passingthrough the channel.

Direct voltages of suitable magnitude are applied to the elementsdisclosed above from a direct voltage source 8. For example, as shown inFIGURE 2, direct voltages of --2000 volts, l volts, -1l50 volts, 300volts, and 0 volt may be applied respectively, to the input 10 andoutput 12 of channel 2, the input 14 and output 16 of channel 4 and theanode 6.

When electrons are introduced to the input end of the multiplier 2, theysuccessively strike the surface of the channel 2 as shown by the path 18in FIGURE 2 and are multiplied through secondary emission. Thismultiplied output current from channel 2 then serves as the inputcurrent to channel 4 which is also multiplied through secondary emissionbeing collected by the anode 6.

It should be understood that the channels 2 and 4 and the anode 6,operate in a vacuum environment.

Although only two channels (2 and 4) have been used in describing thisinvention, it will be recognized that supplementary channels can beadded to provide even greater output currents.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

What is claimed is:

1. An electron multiplier device for amplifying a radiation imageexcitation signal and having an improved output current for a selectedresolution capability comprising a first elongated electron multiplierportion of a crosssectional dimension to establish a selected resolutioncapability for the radiation image and receiving and amplifying aradiation-image excitation signal, and a second electron multiplierportion having a greater crosssectional dimension than at least aportion of said first electron multiplier portion and disposed toamplify a signal from said first electron multiplier portion, each ofsaid electron multiplier portions having a secondary electron emissivesurface and a longitudinal resistance, means including a pair of leadsfrom a voltage source connected to spaced portions of said first portionfor establishing a voltage across the resistance of said first portionfor establishing a strip current through said resistance, and meansincluding another pair of leads from a voltage source connected tospaced portions of said second portion for establishing a voltage acrossthe resistance of said second portion for establishing a strip currentthrough said resistance.

2. The combination of claim 1 in which said second portion has a higherstrip current carrying capability than said first portion and in whichstrip current in said second portion is greater than the strip currentthrough said first portion.

3. The combination of claim 1 in which each of said first and secondportions amplifies said signals in a series of successive stages.

4. The combination of claim 3 in which each of said first and secondportions is cylindrical.

5. The combination of claim 4 in which each of said first and secondportions has a circular cross section.

6. An electron multiplier device for amplifying a radia tion imageexcitation signal and having an improved output current for a selectedresolution capability comprising a first elongated electron multiplierportion of a crosssectional dimension to establish a selected resolutioncapability for the radiation image and receiving and amplifying aradiation-image excitation signal, and a second electron multiplierportion having a greater cross-sectional dimension than any portion ofsaid first electron multilier portion and disposed to amplify a signalfrom said first electron multiplier portion, each of said electronmultiplier portions having a secondary electron emissive surface and alongitudinal resistance, means including a pair of leads from a voltagesource connected to spaced portions of said first portion forestablishing a voltage across the resistance of said first portion forestablishing a strip current through said resistance, and meansincluding another pair of leads from a voltage source connected tospaced portions of said second portion for establishing a voltage acrossthe resistance of said second portion for establishing a strip currentthrough said resistance.

7. An electron multiplier device for amplifying a radi ation imageexcitation signal and having an improved output current for a selectedresolution capability comprising a first elongated electron multiplierportion of a cross-sectional dimension to establish a selectedresolution capability for the radiation image and receiving andamplifying a radiation-image excitation signal, and a second electronmultiplier portion having a greater cross sectional dimension than atleast a portion of said first electron multiplier portion and disposedto amplify a signal from said first electron multiplier portion, each ofsaid electron multiplier portions having a secondary electron emissivesurface and a longitudinal resistance, means including a pair of leadsfrom a voltage source connected to spaced portions of said first portionfor establishing a voltage across the resistance of said first portionfor establishing a strip current through said resistance, and meansincluding another pair of leads from a voltage source connected tospaced portions of said second portion for establishing a voltage acrossthe resistance of said second portion for establishing a strip currentthrough said resistance for supplying electrons emitted by said secondportion in the secondary emission process effectively independently ofany supply thereof via the strip current in said first portion.

8. An electron multiplier device for amplifying a radiation imageexcitation signal and having an improved output current for a givenresolution capability comprising a first elongated electron multiplierportion of a cross-sectional dimension to establish a selectedresolution capability for the radiation image and receiving andamplifying a radiation-image excitation signal in a series of successivestages, and a second electron multiplier portion disposed to amplify asignal from said first electron multiplier portion in a series ofsuccessive stages, each of said electron multiplier portions having asecondary electron emissive surface and a longitudinal resistance, meansincluding a pair of leads from a voltage source connected to spacedportions of said first portion for establishing a voltage across theresistance of said first portion for establishing a strip currentthrough said resistance, and means including another pair of leads froma voltage source connected to spaced portions of said second portion forestablishing a voltage across the resistance of said second portion forestablishing a strip current through said resistance, said secondportion having a higher strip current carrying capability than saidfirst portion, and said strip current through said resistance of saidsecond portion being greater than the strip current through saidresistance of said first portion.

9. An electron multiplier device for amplifying a radiation imageexcitation signal and having an improved output current for a givenresolution capability comprising a first elongated electron multiplierportion of a crosssectional dimension to establish a selected resolutioncapability for the radiation image and receiving and amplifying aradiation-image excitation signal in a series of successive stages, anda second electron multiplier portion disposed to amplify a signal fromsaid first electron multiplier portion in a series of successive stages,each of said electron multiplier portions having a secondary electronemissive surface and a longitudinal resistance, means including a pairof leads from a voltage source connected to spaced portions of saidfirst portion for establishing a voltage across the resistance of saidfirst portion for es tablishing a strip current through said resistance,and means including another pair of leads from a voltage sourceconnected to spaced portions of said second portion for establishing avoltage across the resistance of said second portion for establishing astrip current through said resistance for supplying electrons emitted bysaid second portion in the secondary emission process effectivelyindependently of any supply thereof via the strip current in said firstportion, said second portion having a higher strip current carryingcapability than said first portion, and said strip current through saidresistance of said second portion being greater than the strip currentthrough said resistance of said first portion.

10. An electron multiplier portion device comprising a plurality ofelectron multiplier portions disposed in serial relationship, a firstelectron multiplier portion in the plurality being disposed to receivean excitation signal, each of the electron multiplier portions in saidplurality having a secondary electron emissive resistive surface, meansfor connecting leads from a voltage source to two spaced areas on eachof the portions for producing along each thereof a strip current, eachmultiplier portion of the plurality having a higher strip currentcarrying capability than each preceding multiplier portion and beingdisposed to amplify the output of the preceding multiplier portion, thecurrent between leads of a succeeding portion being higher than thecurrent between leads of a preceding portion.

11. An electron multiplier portion device comprising a plurality ofelectron multiplier portions disposed in serial relationship, a firstelectron multiplier portion in the plurality being disposed to receivean excitation signal, each of the electron multiplier portions in saidplurality having a secondary electron emissive resistive surface, meansfor connecting leads from a voltage source to two spaced areas on eachof the portions for producing along each thereof a strip current, eachmultiplier portion of the plurality having a greater cross-sectionaldimension and a higher strip current carrying capability than eachpreceding multiplier portion and being disposed to amplify the output ofthe preceding multiplier portion, the current between leads of asucceeding portion being higher than the current between leads of apreceding portion.

References Cited UNITED STATES PATENTS 2,160,798 5/ 1939 Teal 313-1052,216,282 10/ 1940 Schwartz et al. 313105 3,176,178 3/1965 Goodrich etal. 313--104 3,225,239 12/1965 Thompson 313l03 10 3,321,660 5/1967Ramberg 313-95 X FOREIGN PATENTS 582,428 12/1924 France.

15 ROBERT SEGAL, Primary Examiner U.S. Cl. X.R. 313--95, 105

